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-   -   What's happening with residuals? (http://www.cfd-online.com/Forums/openfoam-solving/96414-whats-happening-residuals.html)

plm January 22, 2012 14:58

What's happening with residuals?
 
1 Attachment(s)
Hey all,
This may sound like a really silly question, but I'm wondering if someone can take a look at the attached file and tell me what's happening with residuals.

I don't really understand how something can converge like this and then the solution get worse and get stuck at the end...?

Is this a consequence of my particular case setup or is there a more general reason? Is this even a problem, or are my results from the point of most converged valid?

Hoping someone can shed some light on this.
Thanks in advance,
plm

zhernadi January 27, 2012 02:39

fvSolution
 
Hello RW,

I think your simulation is converged based on the convergence criteria. In some OpenFOAM tutorials, the default convergence criteria are using absolute tolerances of 1e-5 or 1e-6, so equations will not be solved if the initial residuals are below these thresholds. However, these settings can be changed in system/fvSolution for every variables with the 'tolerance' setting.

Zoltan

plm January 27, 2012 04:21

Zoltan,
Thanks for the reply.
I am a bit dubious about the above results and don't really trust them myself but wondered what anyone else had to say about it.

I managed to get this case to converge 'properly' (i.e. without going back up at the end) by increasing the relaxation of pressure.

Cheers
plm


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